Cementing float shoe

ABSTRACT

A float valve for a well casing comprises a fixed ring or seat threaded onto the wall of a generally cylindrical shell and receiving a tubular boss to which the ball cage is threaded. The cylindrical boss and the cage are anchored on the shoe casing by a plurality of shear pins so that they may be dislodged by the application of downward over-pressure in the event the valve becomes plugged. A fluted ring is provided beyond the aforementioned fixed ring to intercept the boss and thereby retain the valve while permitting fluid circulation through the flutes.

United States Patent [1 1 Falcuta [451 Sept. as, 1973 1 CEMENTING FLOAT SHOE I [75] Inventor: Persiu Falcuta, Burcuresti, Romania [73] Assignee: Grupul Industrial Pentru Foraj si Extractia Titeillului Bucuresti, llfor, Romania [22] Filed: Nov. 19, 1971 [21] Appl. No.: 200,348

[30] Foreign Application Priority Data Westall 4. 166/224 X Allen 137/71 X Primary ExaminerMartin P. Schwadron Assistant ExaminerRichard Gerard Attorney-Karl F. Ross 57 ABSTRACT A float valve for a well casing comprises a fixed ring or seat threaded onto the wall of a generally cylindrical shell and receiving a tubular boss to which the ball cage is threaded. The cylindrical boss and the cage are anchored on the shoe casing by a plurality of shear pins so that they may be dislodged by the application of downward over-pressure in the event the valve becomes plugged. A fluted ring is provided beyond the aforementioned fixed ring to intercept the boss and thereby retain the valve while permitting fluid circula- [56] References Cited tion through the flutes.

UNITED STATES PATENTS 2,204,340 6/1940 Bradshaw 137/71 X 1 Claim, 5 Drawing Figures [1mm f 7 PATENTED 3E?! PERSIU FALCUTA INVENTOR By. K r RossAitOtnGY CEMENTING FLOAT SHOE FIELD OF THE INVENTION The present invention relates to a shoe adapted to be provided on a drill string and having a float valve and, more particularly, to a cementing float shoe adapted to be used on oil and gas well casing and cementing systerns.

BACKGROUND OF THE INVENTION An oil and gas well casing may be provided with socalled cementing shoes which are threaded onto the lower end of a casing string and accommodate a float valve permitting circulation only in one direction. In general the conventional shoes provided with float valves have the disadvantage that, once the float valve is plugged or blocked, circulation of fluid beyond the valve is prevented and the system becomes inoperative. It is usually necessary to withdraw the casing string and replace the float valve before fluid circulation can begin again.

OBJECTS OF THE INVENTION It is the principal object of the present invention to provide an improved cementing shoe having a floatvalve but free from the disadvantages mentioned earlier.

Another object of this invention is to provide a floatvalve shoe or unit adapted to be threaded onto a well casing or pipe which eliminates the need for withdrawing the casing string in the event the float-valve becomes plugged or inoperative, and which increases the effectiveness of well casing and cementing operations.

SUMMARY OF THE INVENTION These objects are attained, in accordance with the present invention by providing a float-valve shoe having a generally cylindrical casing, a valve-securing ring anchored in the casing intermediate the ends thereof, a tubular member received in the valve-securing ring and defining a seat for a throat carrier by a cage fixed to this member, the latter member being fluted or provided with angularly equispaced outward projections engageable by a fluted ring spaced below the securing ring and adapted to catch the valve assembly when the latter is dislodged by the application of an excessive pressure by the valve, the assembly being held in place by shear pins which give way upon application of the elevated pressure.

The float-valve is thus fastened to the shoe by adetachable couplingconsisting of the aforementioned shear pins, and includes the detachable seat which is received in part in a fixed seat. The fall of the floatvalve assembly is prevented by the stop ring which spaces the assembly, once released from the fixed ring, from the wall of the casing to prevent obstruction of fluid flow around this assembly.

DESCRIPTION OF THE DRAWING The invention is described below with reference to the accompanying drawing in which:

FIG. 1 is an axial (longitudinal) cross-section through a float-valve shoe according to the invention;

FIG. 2 is an axial cross-sectional view through the fixed ring or seat according to the invention;

FIG. 3 is an axial cross-sectional view of the detachable seat which is received in the fixed seat;

FIG. 4 is a top view of the detachable seat; FIG. 5 is a top view of a stop ring according to the invention.

SPECIFIC DESCRIPTION In the drawing, I have shown a float-valve shoe according to the invention which comprises a tubular cylindrical body I which is adapted to be threaded at its upper end onto the casing string and having a downwardly open generally spheroidal member 2 at its lower end, the member 2 serving to guide the casing as it is lowered and being provided with a cylinder boss threadedly received in the casing I.

The float-valve assembly is represented generally at A and is detachably received in the tubular body 1. This assembly comprises a cage 3 receiving a ball 4 which constitutes the float. The cage 3 is generally cylindrical and is provided with an open upper end and an open lower end and with a plurality of radially inwardly extending ledges adapted to support the ball in its lower position as shown in FIG. 1, while permitting the flow of fluid past the ball in the passages between the ledges. At its upper end, the cage 3 is threaded into a detachable seat 6 and clamps a gasket 9 thereagainst, the gasket being engaged by the ball 4 when the latter is urged upwardly by flotation to seal the casing against upward flow of fluid.

The detachable seat 6 has a tubular boss received within a fixed seat or ring 5 and is held with respect to the fixed seat by an O-ring gasket surrounding the tubular boss. Below the tubular boss there is a largerdiameter portion which is complementarily received in the larger recess of the ring 5 and sealed relative thereto by another O-ring gasket so that an upwardly facing shoulder is formed in the detachable ring 6 and abuts a downwardly facing shoulder of ring 5. Ring 5 is, moreover, threaded into the casing 1 so that it is fixed against axial movement in either direction within this casing. Preferably the casing l is provided with an inwardly extending shoulder against which the ring 5 abuts from above.

The detachable seat 6 which, as noted earlier, is fixed to the cage 3 of the valve, is anchored against downward displacement in the casing by shear pins 7 extending into the casing wall.

Below the detachable seat 6, the assembly is provided with a ring 8 threaded into the casing 1 and having inwardly extending ledges separated by flutes (FIG. 5)

and adapted to intercept the lower portion of detachable seat 6 when the latter is dislodged, the cage 3 passing through the ring 8. The detachable seat 6 is provided with radially extending lobes adapted to rest upon the ring 8.

During normal operation of the device, i.e., in the absence of plugging of the valve, the fluid may pass downwardly through the tubular string,the bottom of which is provided with the casing l. The fluid thus passes through the casing l and the fixed seat 5, the detachable seat 6, the interior of cage 3 and the orifice at the bottom guide 2. Should there be a back pressure upon the fluid or should the downward flow of fluid fail, ball 4 moves upwardly to engage the gasket 9 and prevents Should the valve become plugged or inoperative, an elevated pressure is applied above the valve of a level sufficient to shear pins 7 and dislodge members 3 and 6 as a unit. The fixed seat 5, however, remains in place. The dislodged assembly 3, 6 falls until the outwardly projecting lobes of member 6 (F164) rest upon the inwardly projecting ledges of ring 8 (FIG. the fluid then passing through the flutes of the ring 8 without substantial impediment by the detached valve assembly.

I claim:

1. A float shoe for a well string, comprising an elongated tubular casing adapted to be threaded at an upper end on to said string; a fixed annular seat anchored in said casing at a location above the lower end thereof; a float-valve assembly in force-meeting relationship with said fixed seat and including a detachable annular seat normally received in said fixed seat and having an upwardly facing shoulder bearing against a downwardly facing shoulder formed on said fixed seat, said detachable seat being axially ejectable from said fixed seat in a downward direction, a cage affixed to said detachable seat and extending downwardly therefrom, and a float valve received in said cage; shear pins detachably anchoring said assembly to said casing with said detachable seat received in said fixed seat, said detachable seat being formed with outwardly projecting longitudinal ribs beyond said cage; and a fluted ring anchored in said casing at a location below said assembly when said assembly is held in place by said shear pins, said ring clearing said cage upon dislodgement of said assembly and having inwardly extending ledges intercepting said ribs for supporting said assembly within said casing and permitting fluid flow past said assembly through the flutes of said ring. 

1. A float shoe for a well string, comprising an elongated tubular casing adapted to be threaded at an upper end on to said string; a fixed annular seat anchored in said casing at a location above the lower end thereof; a float-valve assembly in force-meeting relationship with said fixed seat and including a detachable annular seat normally received in said fixed seat and having an upwardly facing shoulder bearing against a downwardly facing shoulder formed on said fixed seat, said detachable seat being axially ejectable from said fixed seat in a downward direction, a cage affixed to said detachable seat and extending downwardly therefrom, and a float valve received in said cage; shear pins detachably anchoring said assembly to said casing with said detachable seat received in said fixed seat, said detachable seat being formed with outwardly projecting longitudinal ribs beyond said cage; and a fluted ring anchored in said casing at a location below said assembly when said assembly is held in place by said shear pins, said ring clearing said cage upon dislodgement of said assembly and having inwardly extending ledges intercepting said ribs for supporting said assembly within said casing and permitting fluid flow past said assembly through the flutes of said ring. 